The present invention relates to an amorphous alloy which is used as a core material for a magnetic head, and a magnetic head with an amorphous alloy.
In magnetic heads conventionally used for magnetic recorders/reproducers, a highly magnetic permeable material having a crystalline structure is employed, such as an Fe-Ni alloy (Permalloy) or an Fe-Si-Al alloy (Sendust). However, the Fe-Ni alloy has a disadvantage, in that its wear resistance is low; and, although the Fe-Si-Al alloy has good wear resistance, it also had disadvantages, in that its mechanical strength, brittleness and plastic processing capacity is low.
The amorphous alloy having no crystalline structure, such as a Co-Fe-Ni-Si-B alloy, has recently been identified as an ideal material for a magnetic head. Such amorphous alloys have excellent magnetic properties, such as high saturation magnetization and low magnetostriction, along with high mechanical strength, good wear resistance and good processing capacity.
However; in general, the magnetic head used for a VTR (video tape recorder) must be stably and rigidly. Therefore, especially the core halves of the magnetic head of a VTR are normally secured each other with a glass adhesive to form the gap. The glass bonding process involved requires heat treatment at a temperature higher than 400.degree. C., and a gradual cooling after heat treatment. However, the amorphous alloys all have their respective crystallization temperatures; and the magnetic properties and, particularly, the effective magnetic permeability of the amorphous alloy are deteriorated by heat treatment at a temperature in the vicinity of the crystallization temperature. Further, the conventional low magnetostriction amorphous alloys contain at least two or more of the magnetic elements comprised of Co, Fe and Ni. Consequently, an induction magnetic anisotropy is produced by the heat treatment, and the magnetic properties of the amorphous alloys are thereby deteriorated. Thus, the conventional amorphous alloys have disadvantages, in that the practicability of using them for the magnetic head of a VTR is low.
Thus, there is a present need for an amorphous alloy whose magnetic properties do not deteriorate after glass bonding; i.e., for an amorphous alloy which has a crystallization temperature higher than the temperature necessary for a glass bonding heat treatment (i.e., higher than 500.degree. C.), whose magnetic properties do not deteriorate, even with the gradual cooling which occurs after heat treatment. If only one of the magnetic elements is contained in the amorphous alloy, the deterioration, after gradual cooling, of the effective magnetic permeability of an amorphous alloy having this composition can be prevented. However, such an amorphous alloy has certain disadvantages, in that the requirements for high saturation magnetization and low magnetostriction cannot be satisfied.
As described above, a magnetic head with an amorphous alloy bonded by a glass adhesive is not yet provided, which magnetic head has high saturation magnetization and low magnetostriction and maintain a high level of effective magnetic permeability.